This invention relates to a method and apparatus for manufacturing ultra-conductive and/or ultra-strong nano-composite wire. While the invention is particularly directed to the art of wire manufacture, and will be thus described with specific reference thereto, it will be appreciated that the invention will have usefulness in other fields and applications including the manufacturing of ultra-conductive and/or ultra-strong sheet metal, bars etc.
Since the discovery of electricity, pure metals were thought to have the lowest resistance to transporting electrical current at room temperature. This defined the upper limits of the efficiency and consequently the size and power consumption of all conventional electric machines and devices. Recently, the discovery of carbon nanotubes (CNTs) introduced a new class of metallic carbon nanotubes based conductors (known as ballistic conductors) that are orders of magnitude better at carrying current than pure metals. Unfortunately, harnessing this potential has not been successful thus far because the nanotubes produced to-date are on the order of few millimeters in length and no one has been able to make practical length segments and/or continuous bundles of wires with these properties. Other attempts at harnessing this potential by forming nano-composite metal/nanotubes matrices starting from powdered metals and/or by molecular level mixing failed to produce gains in the electrical conductivity.
The concept of ultra-low resistivity in copper and other metal nano-composites was theorized in 2004. A group of researchers from ABB Corporation and Stanford University proposed that it may be possible to fabricate carbon nanotubes (CNT)/copper composite materials with ultra-low electrical resistivity. To this end, they developed a theoretical model to estimate the possible gains in the conductivity versus the percent fill factor of the nanotubes in a copper nano-composite matrix. That model assumes ballistic conductance over the full length of single wall carbon nanotubes (SWCNTs) with the following nominal properties: mean length of 10 μm, mean diameter of 1.2 nm, resistance at room temperature of 18 KΩ/tube. This translates into a resistivity of 0.35 μΩ cm for the nanotubes in contrast to 1.67 μΩ cm for copper at room temperature. Based on the model and the properties of the nanotubes they selected, the authors concluded that it is possible to achieve ultra-low resistivity/or a doubling of the conductivity with a 30-40% fill factor of nanotubes. They further concluded that in order to realize these gains, a manufacturing process that is capable of producing the nano-composite matrix would need to be developed. And although the technical challenges that would have to be overcome by the manufacturing process were not identified or discussed in that paper, the authors remarked that at a minimum, the nanotubes would need to be well dispersed, preferably aligned, and well contacted within the matrix. In addition, because copper will not wet the carbon nanotubes (i.e., will not form good electrical contacts with the nanotubes), the authors proposed to aid the process by coating the nanotubes with a coating from a list of materials that are non-carbide forming and thus are suitable for forming low contact resistance between them.
The present invention contemplates new and improved systems and methods that resolve the above-referenced difficulties and others.